Antenna



March 16, 1954 J, EHRBAR 2,672,555

ANTENNA Filed D80. 12, 1950 2 Sheets-Sheet l m LIMIT INVENTOR. Eowmo JEHRB ATTORNEY March 16, 1954 ANTENNA Filed Dec. 12, 1950 a n n n n o a a E. J. EHRBAR 2 Sheets-Sheet 2 INVENTOR. EDWARD J. E HRBAR ATTORNEY.

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Patented Mar. 16, 954

ANTENNA Edward .I. Ehrbar, Cleveland, Ohio, assignor to The Radiart Corporation, Cleveland, Ohio, a

corporation of Ohio Application December 12, 1950, Serial No. 200,336

7 Claims.

This invention relates, as indicated, to an antenna, but has reference more particularly to an improved indoor antenna, which is adapted especially for use in connection with television sets.

In copending application, Serial No. 164, there is disclosed an antenna having a dipole adapted for low wave band reception, and comprising spaced rod-like elements connected to each other by means of an inductance coil.

A primary object of the present invention is to provide a variable tuning means, either capacitive or inductive, for such an antenna for continuously tuning through television channel assignments of 54 to 88 mc., as well as for covering frequency modulation and other high frequency channels.

Another object of the invention is to provide a variable tuning means, either capacitive or inductive, which resonates the inductively loaded dipole to the desired frequency, and provides a means for electrically changing the length of the embodying one form of the invention;

Fig. 2 is a fragmentary elevational view of the central portion of the antenna, in full size scale, and with the rear disk removed to more clearly show the construction;

Fig. 3 is a fragmentary front elevational view of the central portion of the antenna, in full size scale, with the tuning knob removed;

Fig. 4 is a fragmentary cross-sectional view, taken on the line 4-4 of Fig. 2;

Fig. 5 is a fragmentary view, showing the end connection between the dipoles of the antenna;

Fig. 6 is a view illustrating diagrammatically the electrical nature of the invention when the tuning is capacitive;

Fig. 7 is a view similar to Fig. 2, but showing a modified form of the invention, utilizing an inductive tuning means or permeability tuning, and

Fig. 8 is a transverse cross-sectional view taken on the line 8--8 of Fig." '7, and

Fig. 9 is a view illustrating diagrammatically the nature of the invention, when inductive tuning means, as shown in Figs. 7 and 8, is used.

Referring more particularly to Figs. 1 to 6 inclusive of the drawings, the antenna will be seen to comprise a base I, molded from a plastic material, as for example, Bakelite, and having threadedly secured thereto a mast 2 formed of metallic tubing, preferably aluminum tubing.

Mounted on the upper end of the mast 2 is a circular antenna support consisting of a front disk 3 and a rear disk 4, which are molded from a plastic insulating material, such as Bakelite, and are removably secured to each other, as by means of a screw 5, passing through aligned central apertures in the disks, and a nut 6 threadedly secured to the screw 5 and disposed in a countersunk recess I in the front of the disk 3. The disks 3 and 4 are molded to provide radial recesses 8, of semi-circular cross-section, which coact to receive and snugly engage the upper end portion of the mast 2.

The disks 3 and 4 are also molded to provide downwardly extending divergent recesses ll] of semi-circular cross-section, which coact to receive and snugly engage the inner ends of aluminum tubes ll and I2 which form elements of a dipole, which are so dimensioned as to be in resonance electrically with television broadcasting stations in the present high band television allocation or spectrum, such, for example, as channels '7 to 13, inclusive.

Disks 3 and 4 are likewise molded to provide upwardly extending divergent recesses I 3 of semicircular cross-section, which coact to receive and snugly engage the inner ends of aluminum tubes 14 and I5, which form elements of a second dipole, the inner ends of which are spaced from each other.

Disposed within a recess or cavity It in the disk 3, directly above the recesses I3, is an inductance coil I! preferably formed of fine enamelled wire, wound around a core 18, of Bakelite or other suitable material, the ends of the coil being electrically connected to the tubes l4 and. [5 respectively by means of wire connections 19 and 20, which are clamped to the tubes l4 and 15 by means of washers 2|. The washersZlare secured in position by means of. nuts 22, which are threaded into studs 23 which extend diametrically through the tubes. M and I 5 and to the rear face of the disk 3.

The coil H has an inductance which permits the combination of the dipole elements 14 and I5 and the coil I 1 to be in resonance electrically with television broadcasting stations in the present low band television allocation or spectrum, such, for example, as channels 2 to 6, inclusive. The dipole I l-I5 is thus electrically loaded at the center by means of the coil l1.

" The rear end of one of thefstudsfit is fastened to one end of athin brass strap 24, the other end of the strap being fastened to the nut 6.

The rear end of the other stud 23 is fastened to a C-shaped plate 25 of thin brass stock similar to that ;-f-rorn svhich the strap .24 is made, the point of=conneotion being adjacent the periphery of the plate.

The stem or shank of the screw extends for an appreciable distance beyond the nut 5, and has threadedly secured thereto a relatively thick circular brass plate 26 which isrigidly embedded in a disk 21 of insulating material, such as Bakelite. The disk 2'! is provided with a knurled knob 28 formed integrally with the disk, this knob serving as a means for manually rotating the disk, whereby the spacing between the plate 26 and the plate 25 may be varied,

The plates 25 and Y26 are thus electricallyrinsulated from each other and form 'a variable condenser which is in parallel with the inductance coil ll of the'dipole l ii'ii. 'Themanual controller varying the capacitance of theplates '25 an'dl i, which is afforded by the readily. accessible Lknob '28,,provides a means .for continuously tuning through the television channel assignments of 54 to'88 mc. and-may be used to cover FM and other high frequency channels.

Thecapacity ofthe variable condenser resonates'the inductively loaded dipole to the desired frequency, and ,provides a means for electrically changing the length ofthe loaded dipole, without ealtering'its mechanicalstructure. The tuning control is conveniently located and easily operated, and the mechanism is simple in construction and inexpensive to manufacture.

The dipole elements ii and i2 are bent upwardly at their outer ends, and the dipole elements 'M and "i5 are similarly bent downwardly at their outer .en'ds extending downwardly to points spacedfrom .the outer ends of elements 5 I and "i2. Buttons 26,3?ormed or a plastic insulating material, are employed as means for mechanically joining thedipo'le elements H and E2 to the dipole elements Hi andlfi at their ends. From an electrical standpoint, the buttons 29 form the dielectric material for condensers or capacitors, which consist of these buttons and the portions of the dipole elements which they connect. They serve to couple voltage at the ends of the dipole formed by the elements i4, :5, ll, 25 and 26 to the lower dipole made up of the elements ll and 12, that is to say, the di poles are coupled electrically by means oi capacitance established through the insulatingmaterial of buttons 29.

The terminals or contacts 39 and Bi of a transmission line '32 are secured electrically to the tubes Ii and 12, :as by clamping such contacts to the tubes by means of the heads of self-tapping screws 33 which are in threaded engagement with the tubes 1 l and 12. The transmission line 32 is a conventional ione employed to connect the antennatothe television set'or receiver.

In that form of the invention shown in Figs. 7, 8 and 9, the inductance coil ll, which is preferably formed of fine enamel wire, is wound around .a-core .18 of Bakelite or .other suitable material. The core .i8is in the form of a tube containing a powdered iron core, which is movable along the axis of .thetube, so asto vary the inductance of the coil ll. This .movable powdered iron core constitutes an. inductive tun- 4 .invention, herewith -shownrand, described are to be taken as .preferredeaamples of the same,-

each-other [mounted in said discs, an inductance coil-disposed within one of said discs, and connected to said dipole elements, a screw passing through --aligned central apertures in said discs and-connecting said discs to each other, said screw having an extension projecting behind the rear disc, and variable tuning means for said inductance coil, said tuning means "comprising metallic plate secured to there'ar surface of the rear disc and electrically connected to said inductance coil, asecond metallic plate threadedly seemed to "said extension and disposed parallel with said first ip1ate,"and means ior rotating said second plate to vary the spacing between said plates.

2. An antennaas defined in claim 1, in which said-rotating means comprises a knob of insulating material in which't'he second plate is embedded.

3. An antenna, as delined'in claim 2, in which said inductance'coil is connected to said dipole elements by means of screws passing diametrically through the dipole elementsthe rear end one ofsaidscrews being electrically connected to said first plate-and the rear end of the other screw electrically connected to a strip of metal which, in turn, is-electrically connected to the screw which extendsthrough the central apertures in the discs.

4. An antenna, as defined in claim 3, in which said metal'strip is disposed in a recess in said first plate and is coplanar with said plate.

5. In "an antenna for television purposes and the like, a mast, a pair of connected disks of in- 'sulating material mounted 'on said most, dipole elements in spaced relation to "each other mounted in said disks, an inductance coil connecting said "elements and in'series therewith and disposed in one of said disks, a variable capacitance in parallel with said inductance coil, said capacitance comprising spaced metallic plates, and means for varying the spacing between said plates, one o'fisaidiplates being mounted on the front of one of :saiddisks, and the other of said plates being mounted on a third disk disposed in a plane parallel with said plates.

6. An antenna, as defined in claim 5, in which saidother plate is threadedly secured to the ReEerences Cited in the file of this patent UNITED STATES PATENTS Number Name Date D. 156,379 Spirit -1 Dec. 6, 1949 1,762,221 Fitch June 10, 1930 1,934,412 Englund 1 1 Nov. 7, 1933 2,143,658 Morris et a1. Jan. 10, 1939 2,206,820 .Mydlil .July 2, 1940 2,259,628 Feneret al. Oct. 21,1941 2,433,641 I-Ierrick 1 s Sept. 27, 1949 [2,558,487 Hills June 26, 1951 "2,576,128 Lense Nov. 27, 1951 

